Problem: $ { \left[\begin{array}{rr}{2} & {1} \\ {-1} & {1}\end{array}\right]-\left[\begin{array}{rr}{4} & {-2} \\ {-2} & {-2}\end{array}\right] = {?} } $
Solution: To find the difference of two matrices, subtract the corresponding items between each matrix. ${\left[\begin{array}{rr}{2}-{4} & {1}-{-2} \\ {-1}-{-2} & {1}-{-2}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{-2} & {3} \\ {1} & {3}\end{array}\right]}$